Digitalization is expected to enable construction sites to be connected and provide information for smarter and safer operation decisions. Connected sites emergent integrated simulation architecture to simulate the interaction between actors in different layers from the operation layer to the system layer. This paper proposes a distributed event-based asynchronous simulation platform that enables simulating the system modules with different simulation approaches from different perspectives and aggregates the results in an orchestrating manner. The proposed integrated simulation framework can be used as a decision-support system for optimizing the design and operation of complex systems such as construction sites. A quarry site is used as a use case to illustrate the applicability and benefits of the proposed simulation framework.